Lung cancer occurs when cells in the lung divide without control or order. Normally, cells divide in a regulated manner. If cells keep dividing uncontrollably when new cells are not needed, a mass of tissue forms, called a growth or tumor. The term cancer refers to malignant tumors, which can invade nearby tissues and can spread to other parts of the body. A benign tumor does not invade or spread.

Lung cancers that start in the lungs are divided into two types:

Non-small cell lung cancer—This type generally grows and spreads more slowly. Non-small cell lung cancer accounts for the majority of the lung cancer cases that are diagnosed each year in the United States.
The most common types of non-small cell lung cancer are squamous cell cancer and adenocarcinoma.

Small cell lung cancer—This type generally grows more quickly. It is more likely to spread to other parts of the body.

Revision Information

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.